Class8.L-5. Synthetic Fibres and plastics

EXERICE

A.Choose the correct option for each of the following .

1)Fibre obtain from chemical treatment of wood pulp is – b)Rayon

2.A synthetic fibre used for making woollen clothes –b)Acrylic

3.Which of the following is biodegradable?- d)Paper bags

4.Which of the following can be used as a substitute for glass ?-b)Perspex

5.Nylon was first prepared from – a)Coal ,water and air

B. State whether the following statements are True(T) or False(F).

1.Polymer can have only linear structure . (F)

2.Thermosetting plastics are used to make unbreakable dinnerware . (T)

3.Acrylic  fibres burn with sooty flame . (T)

4.Synthetic fibres are resistant to moths and moulds. (T)

5.Plastics are good conductors of electricity . (F)

C.Fill in the words with correct words.

1.Synthetic fibres are also referred to as –man made fibres .

2.Plastics are –inflammable .

3.Non-biodegradable wastes should be thrown in the – blue bins.

4.Regenerated fibre is another name for –rayon.

5.Lycra is the popular name for –Spandex.

D.Match the following .

Column A	Column B
a)Polyester	3)PET jars and bottles
b)Nylon	4)Parachutes
c)Rayon	5) Obtain from wood pulp
d)Acrylic	1.Blankets
e)Polystyrene	2.For making disposal cups

E. Name the following .

1.The fibre that is also known as artificial silk- Rayon.

2.The synthetic fibre that derives  its name from two cities –Nylon.

3.This is called the small unit of a polymer- Monomer.

4.A mixture of terylene and cotton –Terrycot .

5.The plastics that don’t soften much on heating – Thermosetting .

F.Answer the following questions briefly.

1.What is polymerization.

ANS:-The process in which small monomers link together to form a long chain polymers is called Polymerization.

2.Why is rayon called a regenerated fibre?

ANS:-Rayon is prepare from cellulose that is broken down and then reformed , so it is also called regenerated fibre.

3.Write the properties and uses of acrylic.

ANS:-

Properties:

a) It is light, soft and warm with a wool-like feelings.

b) It is resistant to moths and other insects.

Uses: It is widely used for making sweaters, shawls and blankets.

4.Why do we use containers made of plastic to store water and chemical ?

ANS:-Plastics do not react with water and air, thus do not corrode or rust easily. So, they are used for  storing chemicals and other materials .

5.What is PET ? Give its two uses.

ANS:-PET(Polyethene tetraphthalate) is one of the common form of Polyester fibre.

Uses: PET is used for making bottles , utensils and films.

G.Answer the following questions in details.

 1.List the advantages and disadvantages of synthetic fibres.

ANS:-

Advantages	Disadvantages
1)They are strong and elastic. 2)They are resistant to moths and moulds. 3.They dry quickly and are less expansive. 4)They are wrinkle-resistant. 5)They can be dyed in a variety of colours.	1) They do not absorb sweat like natural fibres do. 2) They should be ironed carefully as they may get damaged by high temperature. 3)They catch fire more easily than cotton or wool. 4)They do not allow air to pass freely through them and stick to the body of the person on sweating.

2.What are plastics ? Write the general properties of plastics.

ANS:-Plastics are synthetic polymer commonly derived from petrochemicals. With respect to heat there are two types of plastics: a)Thermoplastics and b)Thermosetting plastics.

Properties:-

a)Plastics are insoluble in water hence they are used to make bucket , bottle to store water.

b)Plastics do not react with water and air, thus do not corrode or rust easily. So, they used to store chemicals and materials.

c)Plastics catch fire easily, so they are inflammable.

d)Plastics are poor conductor of electricity. Hence they are used as a covering for electric wires, cables.

e)Plastics are poor conductors of heat . Hence they are used for making handles of cooking utensils.

3.Differentiate between thermoplastic and thermosetting plastics?

ANS:-

Thermoplastic	Thermosetting plastic
1)It can be melted easily on heating and can be moulded  again and again into different shapes. 2)Different types of this are: Polythylene, Polypropylene, Polystyrene and polyvinyl chloride(PVC). 3)Pipes for transporting water ,Containers ,hand gloves, Covering of electric wires etc are made from thermoplastic.	1)It is do not soften much on heating and can be moulded only once .Even at high temperature they can maintain their shape and size. 2)Different types of this are :Bakelite, duroplast,melamine and epoxy resin. 3)Unbreakable dinnerware , plugs, switches ,handles of tea kettles etc are made from this.

4.What are harmful effects of excessive use of plastics ?

ANS:-Some of the harmful effects of excessive use of plastics are:

a)Burning of plastics releases poisonous gases into the atmosphere causing air pollution.

b)Plastics prevent the replenishment of ground water and percolation of water into the soil.

c)Recycled plastic bags cause poisonous dyes to get absorbed into the food item stored in them , which are harmful for health .

d)Plastic bags consumed by animals along with the leftover food causes illness and sometimes leads to death.

d)Careless disposal of plastic bags blocks the drains resulting in the overflow of wastewater.

5.Mention a few measures that can be taken to prevent pollution caused by plastics.

ANS:-Some of the measures that can be taken to prevent pollution caused by plastics are:

a)Reduce dependence on plastic bags and on other items made of plastic.

b)Encourage reuse and recycling of plastics.

c)Buy products with less plastic packaging.

d)Use biodegradable plastics instead of non-boidegradable plastics.

e) Plastics should not be dispose of in the seawage system, on the streets or on the pavements .It clogs the drains and causes wastewater to overflow.

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